As a method for improving physical properties, appearance and feeling of hair by making hair-component materials penetrate inside of the hair, it has hitherto been proposed to supplement the hair with decomposed matters and derivatives of hair such as collagen, keratin or the like which are similar to the components of hair. However, such method has failed to obtain satisfactory effects.
On the other hand, there has been known a technique for strengthening hair by using an alkyltrialkoxysilane for the hair treated with an alkali (for example, refer to JP-A-61-7). Also proposed is a method for protecting and strengthening keratin substances in nails, hair or the like by applying thereto an organic silicon compound obtained by partially or totally hydrolyzing an organic silicon compound or the like and polymerizing the resulting hydrolysate (for example, refer to JP-A-2000-510167 and JP-A-2002-97114).
However, such techniques have the problems that the organic silicon compound loses its effect upon washing and that the feeling of the surface of keratin becomes different from its inherent feeling since the compound exists only on the surface of keratin.